Fix SyncManager initialization failure crash.

chrome/browser/sync/glue/sync_backend_host.cc

Index: chrome/browser/sync/glue/sync_backend_host.cc
diff --git a/chrome/browser/sync/glue/sync_backend_host.cc b/chrome/browser/sync/glue/sync_backend_host.cc
index 295bb8c5f7ea6b4d89007e75e9ce6f0fe54bda97..89feb67aaa86b289d91680341a85160135a3ccfb 100644
--- a/chrome/browser/sync/glue/sync_backend_host.cc
+++ b/chrome/browser/sync/glue/sync_backend_host.cc
@@ -846,6 +846,12 @@ void SyncBackendHost::Core::OnInitializationComplete(
     bool success,
     const syncer::ModelTypeSet restored_types) {
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
+
+  if (!success) {
+    sync_manager_->RemoveObserver(this);
+    sync_manager_.reset();

[tim (not reviewing), 2012/07/31 19:40:26]

The main danger with this is that SyncManager needs to make sure it tears down
what it needs to if it detects failure. We actually carefully tear things down
in StopSyncingForShutdown and ShutdownOnSyncThread, but this will mean we just
rely on declaration orders / destructors. 

I'd recommend we move the call to set up connection_manager_ to *after* we
return false for good measure -- if we created that and (for example) set up the
NetworkChangeNotifier, we'd be in danger of hanging on shutdown since we'd
return false but never call TerminateAllIO (because we'd never call
StopSyncingForShutdown).

I'd also recommend, if we can, that we call
sync_manager_->ShutdownOnSyncThread() before reset here.

[rlarocque, 2012/07/31 20:14:07]

Good idea.  Done.
Done.

+  }
+
   host_.Call(
       FROM_HERE,
       &SyncBackendHost::HandleSyncManagerInitializationOnFrontendLoop,
@@ -1051,19 +1057,22 @@ void SyncBackendHost::Core::DoRefreshNigori(
 
 void SyncBackendHost::Core::DoStopSyncManagerForShutdown(
     const base::Closure& closure) {
-  DCHECK(sync_manager_.get());
-  sync_manager_->StopSyncingForShutdown(closure);
+  if (sync_manager_.get()) {
+    sync_manager_->StopSyncingForShutdown(closure);
+  } else {
+    sync_loop_->PostTask(FROM_HERE, closure);
+  }
 }
 
 void SyncBackendHost::Core::DoShutdown(bool sync_disabled) {
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
-  if (!sync_manager_.get())
-    return;
+  if (sync_manager_.get()) {
+    save_changes_timer_.reset();
+    sync_manager_->ShutdownOnSyncThread();
+    sync_manager_->RemoveObserver(this);
+    sync_manager_.reset();
+  }
 
-  save_changes_timer_.reset();
-  sync_manager_->ShutdownOnSyncThread();
-  sync_manager_->RemoveObserver(this);
-  sync_manager_.reset();
   chrome_sync_notification_bridge_ = NULL;
   registrar_ = NULL;